1. Field of the Invention
The invention is related to a transmission system comprising a transmitter for deriving words of coded data symbols from input data symbols, and for applying a coded signal derived from the words of coded data symbols to a transmission channel, a receiver for receiving the coded signal from the transmission channel comprising a decoder for deriving said words of coded data symbols from the received coded signal
2. Description of the Prior Art
The invention is also related to a recording system and a receiver.
A transmission system according to the preamble is known from U.S. Pat. No. 4,620,311.
Such transmission system can e.g. be applied for the transmission of digital symbols via the public telephone network, for the transmission of multiplex signals between exchanges or for the transmission of digital signals in mobile radio systems. Said recording systems can be used for the recording and reproduction of digital symbols using magnetic tapes or magnetic discs such as hard discs or floppy discs. Said recording system can also be used with optical or opto-magnetic discs.
In order to transmit the input data symbols via the transmission channel, said input data symbols are often transformed into coded data symbols by the transmitter. Coding is performed in order to obtain certain desired properties of the frequency spectrum of the coded signal. An often desired property of the frequency spectrum of the coded data signal is that it does not contain any DC component, because a number of common transmission channels are not able to pass DC. Another reason for coding the input signal is to obtain the possibility of correction of transmission errors. These transmission errors can be caused by thermal noise and all kinds of interference.
To enable the use of a relatively easy decoder often so-called block codes are used. In such a block code, words of input data symbols are transformed into words of coded data symbols. In the block code according to the above mentioned U.S. patent, the words of input data symbols comprise 8 bits, and the block of coded data symbols comprises 10 bits.
In the prior art system the words of coded data symbols are derived from the coded data signal by slicing said coded data signal. In this way an optimum performance can not be obtained because the redundancy present in the words of coded symbols is not exploited for reduction of the error rate.